1. Field of the Invention
The present invention relates generally to mechanical devices used in surgical procedures to obtain ligation or hemostasis, and more particularly, to low profile tools that can apply a pre-formed, spring loaded ligation clip used during surgery to clamp around a vessel or duct, such as the cystic duct, and thereby obtain ligation.
2. Description of the Prior Art
It will be appreciated by those skilled in the art that the use of ligation clips to control bleeding during surgical procedures is will known. As described, for example, in U.S. Pat. Nos. 4,976,722 and 4,979,950 prior art clips are generally formed of metal wire, usually a titanium alloy, having a “U-shaped” rectangular cross-section. Such prior art clips often include a grooved pattern machined into the inner or clamping surfaces of the clip, in an attempt to enhance the ability of the clip to remain in position after it is closed around the vessel. Application of the clip to the vessel is normally effected by means of a crushing action produced by a clip applier, such as the disclosed in U.S. Pat. No. 5,030,226. Such crushing actions, of course, permanently deform the clips, making them difficult to remove or re-position.
Prior art surgical ligation clips have several inherent problems. For example, the force applied by the clip to the vessel can be variable and inconsistent from one clip to the next, because of the variation in crushing force applied to the clip by the user. Further, prior art clips have a tendency to slip off the end of the blood vessel stub (i.e., perpendicular to the axis of the vessel) to which it has been applied, because of the low coefficient of friction associated with the clip, and lack of adequate restraining force provided by the clip. Because of this, separation of the clip from the vessel to which it has been applied, after the wound has been closed, is not uncommon. A related problem found in the prior art is the fact that the ligating or restraining force offered by the crushed clip varies along the length of the clip, decreasing toward the open end. Thus, the section of the vessel near the open end of the clip can be inadequately ligated.
It is also common in the prior art to actually form and crush the clip only at the time of its application to the targeted blood vessel. It is often required that the vessels of 4 mm and larger diameter be ligated. Because most clips of the prior art have no spring action it is required that the inside clearance dimension of the clip, prior to crushing, be larger than the vessel. This does not lend itself to clip applier designs that will pass through small 5 mm trocars. The applier must be inserted through a trocar placed through the patient's external tissues and into the surgical field. Thus, prior art ligation clip appliers used in laparoscopic procedures universally consist of a 10 mm diameter clip applier that can fit only through a trocar having a 10 to 11 mm diameter entry port. Because one goal of laparoscopic surgery is to minimize the size of the entry wound, a surgical ligation clip and clip applier that can be used within a 5 mm or even a 2.5 mm diameter trocar port is highly desirable.
New minimally invasive surgical procedures and the need for less invasiveness for current procedures require the development of smaller and smaller devices. The harvesting of saphalous veins and certain cardiovascular procedures would benefit from reduced diameters trocars, below 3 mm diameter.
To address these problems a new spring action surgical clip was designed, as illustrated in FIGS. 1 and 2 in U.S. Pat. No. 5,593,414, which is assigned to the assignee of the present invention and is incorporated herein by reference. This clip has a vessel clamping arm, a vessel support member, and at least one tension coil integrally joining the arm and support member. The clip is pre-formed so that in its equilibrium state, it can be easily placed within the surgical field, including through an endoscopic trocar port with as little as 5 mm diameter. After the clip is placed proximate the blood vessel or duct to be clamped, the clamping arm is moved from its equilibrium position to a position under higher tension, allowing positioning of the vessel between the arm and support member. When correct placement and positioning is achieved, the arm is released and, as the arm tends to move back towards its equilibrium position, it clamps the vessel between the arm's curved lower surface and the supporting upper surface of the vessel support member.
To enhance the performance of the tension coil(s), the vessel support member includes first and second arms, one of which terminates in a 180° bend section. Minimal cross-sectional area of the clip is achieved by substantially longitudinally aligning the vessel support member, the clamping arm, the 180° bend section, and the tension coil.
The clamping arm is pre-formed into an equilibrium that generally aligns with the horizontal plane of the support member. A second embodiment of the clip pre-loads the clamping arm into a pre-loaded equilibrium position where the free end of the arm rests against the upper surface of the support member.
There exists a relationship between the diameter of the trocar (hence the applier tube) and the maximum diameter of a vessel that can be ligated. Older crush clip technology limits the ratio of wound size to maximum diameter to be ligated to greater than 2. That is, to ligate a 5 mm vessel a puncture wound of 10–12 mm is required. U.S. Pat. No. 5,593,414 teaches the method of using a spring clip that is inserted into the surgical field in the closed state, opened over a vessel, the diameter of which has been reduced, or preclamped, by the tool, and closed over the preclamped vessel. This method allows an entry wound to vessel diameter of 1 or smaller. Thus, a 5 mm vessel can be ligated through a 5 mm trocar, substantially less invasive as compared to the older crush clip technology. For a trocar diameter of 2.5 mm the clip can be scaled down to approximately half size on the wire diameter, coil height, and length and still supply an acceptable ligation force on a 2.5 mm vessel.
Unfortunately, several problems are encountered in applying the spring-action ligation clip of U.S. Pat. No. 5,593,414 to a vessel through a 5 mm or small trocar port. First, the nominal 5 mm cross-section of the clip that is inserted through the trocar places severe design restrictions on any applier mechanism. Second, care must be taken so that the elastic limit of the spring material is not exceeded when the clip is opened up so that it can be placed over the vessel diameter. For the titanium wire of diameter 0.75 mm, for example, lifting the distal end of the center leg of the spring much above a few mm will exceed the elastic limit. Secondly, these spring clips are small and compact and owing to the pre-load, have a great deal of energy stored in the spring. As these clips are opened to place them over a vessel the stored energy increases substantially, in some cases more than doubling. This energy makes controlling the clip, to insure proper installation, difficult. Undesirable translation or rotation can result in misplacement or dropping of the clip inside the body.
What is needed, then, is a spring clip that includes a means that allows positive control of the clip during the installation process and a clip applier tool that can be used to place a pre-formed spring action ligation clip around a large diameter vessel without permanently deforming or weakening the clip, one that will compress, without crushing the vessel, and yet be small enough to use in through a 5 mm or smaller trocar. Also needed is a design which will avoid the mechanical difficulty of opening the clips prior to placement of the clips on the vessel.
Another approach which has been proposed to provide smaller diameter endoscopic clip application is that of U.S. Pat. No. 5,601,573 to Fogelberg et al. Fogelberg et al. still struggles with the complex manipulation required to advance the clip in a closed position and then open the clip prior to placement. Fogelberg et al. also has an overly-complex multi-stage trigger arrangement for actuation of the jaws and the clip advancement mechanism. The present invention presents several improvements over Fogelberg et al. including: (1) advancement of the clips in their open position rather than a closed position; and (2) a smooth single stage trigger action which simultaneously closes the jaws and advances the fowardmost clip into the jaws. Another difference between the present invention and Fogelberg et al., is that Fogelberg pushes a stack of clips, whereas the present invention individually engages and pushes each clip simultaneously, thus yielding better control of the clips.